1. Field of the Invention
This invention relates generally to an electric plug connector. More particularly, this invention relates to a flexibly foldable electric plug connector for connecting to associated internal circuits wherein the electric plug connector is configured to improve the foldable connection of the plug thus reducing the space occupied and providing improved electric connection and strengthening construction whereby the electric plug connector connected to the associated internal circuits is suitable for continuous portable operation.
2. Description of the Prior Art
Current trend in the miniaturization of electronic devices and computers imposes higher demand on the form factors of the electric power connectors, particularly those of the plug-in types of connectors. The demands on form factors include the requirements that these types of connectors be made such that they have smaller size, less weight, convenient for shipment. More importantly, they must be durable in order to sustain long term portable operation on a continuous basis.
These demands cause special challenges to the design of the plug-in type of connectors due to the fact that the plugs for making electrical connection of this kind of connectors are vulnerable as the plugging legs usually extend outside of the body of the connectors and can be easily damaged without protection. This could cause serious concerns for the operation of the portable computers. A specific need in the operation of a portable notebook computer is to carry along a rechargeable battery package which generally comprises a plurality of rechargeable batteries contained in an enclosure box which has the charging circuits and a plug-in connector to plug into the electrical outlet for recharging. It is highly desirable for the battery package to be small, light, and easy to be conveniently portable. On the other hand, this package has to be very durable and sturdy and the electric contacts between the charging circuits and the plug-in connector have to be reliably maintained so that the package is suitable for the portable operation with high degree of reliability.
Many of the conventional electrical connectors including some of these plugs for the battery chargers are made with a structure such that they are foldable. This types of battery charger generally is constructed with the shape of a box containing inside the box the circuits for charging the batteries. The battery charger also has a pair of outwardly extended electrical plugging legs for connecting to an external power supply. When the electrical connector is plugged into an external power supply, an electrical connection is established with an internal contact-unit through which the electrical power is provided to the internal circuits.
One example of these chargers is Sony's battery charger Model BC-3K4 which has a side-way foldable electrical plug as shown in FIG. 1 as a battery charger 10. The battery charger 10 comprises charging circuits 12 for charging the re-chargeable batteries (not shown) which are contained in a containing box 15. The containing box 15 has a concave confinement 18 containing a foldable electric plug unit 20 which includes a pair of outwardly extending plugging legs 22 for plugging into the external power supply (not shown). The extending plugging legs 22 are attached to a foldable fixture 24 which is attached to the bottom of the concave confinement 18 by use of a pivotally rotatable attachment spring 28. The foldable electric plug unit 20 can thus pivot the attachment spring 28 and the outwardly extended electric plugging legs 22 can be rotated along the A--A' direction to be either folded into the concave confinement 18 when not in use or can be deployed by rotating toward the A'--A direction such that the plugging legs 22 are fully outwardly extended to be plugged into an external power supply (not shown).
In order to establish an electric contact between the extending plugging legs 22 and the internal circuits 12, the electric plug unit 20 also has a pair of internally extending plates 30. Each of the internally extending plates 30 is electrically connected to a corresponding outwardly extending electric plug 22 and mechanically attached to the foldable fixture 24. The internally extending plates 30 can therefore rotate along the A--A' direction together with the outwardly extending plugging legs 22 and the foldable fixture 24 pivot the attachment spring 28. When the foldable fixture 24 is rotated toward the A'--A direction to unfold the outwardly extending plug 22, the internally extending plates 30 is moved to engage a pair of spring contact plates 32. The internally extending plates 30 first push the pair of the contact spring plates 32 which then spring back to tightly engage the internally extending plates 30 to establish an electric contact.
In order to assure that a good electric contact is established, the spring contact plates 32 assert a spring force which pushes the spring contact plates 32 to tightly engage the internally extending plates 30. The spring contact plates 32 thus provide a mechanical means for establishing and maintaining good electric contact. Sony's BC-3K4 battery charger however suffers several disadvantages. First, the spring contact plates may gradually lose its spring force under prolong use which may cause it to suffer mechanical fatigue. The loss of the spring force may further cause inadequate contact causing excessive heat and electric sparks to be generated at the contact point between the internally extending contact plate 30 and the spring contact plates 32. The electric contact may be further degraded because the heat and the sparks often cause the surfaces of these contact plates to oxidize thus forming an oxidation film on these surfaces which further prevent a good electric contact to be established.
Secondly, since the internally extending plates 30 have to rotate inside the containing box 15 when the foldable fixture 24 pivots the attachment spring 28 when the outwardly extending electric plugging legs 22 are to be folded or unfolded, more space has to be used for the movement inside the containing box 15. Even though the space required to allow the internally extending contact plates 30 to rotate may seem small and insignificant, for the purpose of being portable with a notebook or palm-top computers, every inch saved may often become important in order to reduce the weight and size of these battery chargers. Sony's design may therefore impose a limitation preventing the battery charger to become further miniaturized due to this requirement of extra space for internal rotation of the internally extending contact plates 30.
Thirdly, Sony's battery chargers and many other foldable electric plugs of similar designs have another major difficulty in the mechanical design. The foldable fixtures usually have weak mechanical structure for attaching to either the containing box or other structures of the electric plug connector. The requirement that the plugs have to foldable often imposes a limitation on the attachment mechanism which must be pivotally moveable. The attachment mechanism is frequently being designed as a single point or to the most single axial, two-point attachment mechanism. The weak attachment structure may cause the foldable unit to be less reliable and may also affect the establishment or maintenance of a good electric contact.
Therefore, there is still a need in the art of design and manufacture of electric plug connector to provide a foldable electric plug connector which is durable, compact and capable of reliably establishing and maintaining good electric contact.